Differential amplifier circuit

Abstract

Externally input voltages IN(−) and IN(+) are input to the input terminal of a differential amplifier unit ( 1 ) not directly, but after being shifted by voltage shift units ( 2, 3 ). The input voltages IN(−) and IN(+) are decreased by α when they are at high level, and by β when they are at low level. In this case, α>β. The voltage difference of the external input voltage IN between high and low levels is relatively reduced, and then the external input voltage IN is input to the differential amplifier unit ( 1 ). This widens the substantial in-phase input voltage range in the differential amplifier unit ( 1 ).

What is claimed is:  
     
       1. A differential amplifier circuit comprising: 
       a differential amplifier unit which has first and second input terminals and differentially amplifies first and second input signals respectively input to the first and second input terminals;  
       a first voltage shift unit which is connected to a first external input terminal and the first input terminal, decreases the first external input signal by a first voltage when a first external input signal input from the first external input terminal is at high level or decreases the first external input signal by a second voltage smaller than the first voltage when the first external input signal is at low level, and supplies the resultant first external input signal as the first input signal to the first input terminal; and  
       a second voltage shift unit which is connected to a second external input terminal and the second input terminal, decreases the second external input signal by the first voltage when a second external input signal input from the second external input terminal is at high level or decreases the second external input signal by the second voltage when the second external input signal is at low level, and supplies the resultant second external input signal as the second input signal to the second input terminal.  
     
     
       2. A circuit according to  claim 1 , wherein 
       said first voltage shift unit comprises  
       a first MOSFET having a drain connected to a first power supply terminal, a gate connected to the first external input terminal, and a source connected to the first input terminal, and  
       a second MOSFET having a drain connected to the first input terminal, a gate which receives a first predetermined potential, and a source connected to a second power supply terminal,  
       said second voltage shift unit comprises  
       a third MOSFET having a drain connected to the first power supply terminal, a gate connected to the second external input terminal, and a source connected to the second input terminal, and  
       a fourth MOSFET having a drain connected to the second input terminal, a gate which receives the first predetermined potential, and a source connected to the second power supply terminal, and  
       back gates of the first, second, third, and fourth MOSFETs are connected to the second power supply terminal.  
     
     
       3. A circuit according to  claim 1 , wherein said differential amplifier unit comprises 
       a current source having one terminal connected to the first power supply terminal,  
       a fifth MOSFET having a source connected to the other terminal of the current source, and a gate connected to the first input terminal,  
       a sixth MOSFET having a source connected to the other terminal of the current source, and a gate connected to the second input terminal,  
       a seventh MOSFET having a drain and gate connected to a drain of the fifth MOSFET, and a source connected to the second power supply terminal, and  
       an eighth MOSFET having a drain connected to a drain of the sixth MOSFET, a gate connected to the gate and drain of the seventh MOSFET, and a source connected to the second power supply terminal.  
     
     
       4. A circuit according to  claim 1 , wherein said differential amplifier unit comprises 
       a current source having one terminal connected to the first power supply terminal,  
       a first bipolar transistor having an emitter connected to the other terminal of the current source, and a base connected to the first input terminal,  
       a second bipolar transistor having an emitter connected to the other terminal of the current source, and a base connected to the second input terminal,  
       a third bipolar transistor having a collector and base connected to a collector of the first bipolar transistor, and an emitter connected to the second power supply terminal, and  
       a fourth bipolar transistor having a collector connected to a collector of the second bipolar transistor, a base connected to the collector and base of the third bipolar transistor, and an emitter connected to the second power supply terminal.  
     
     
       5. A circuit according to  claim 2 , wherein said differential amplifier unit comprises 
       a current source having one terminal connected to the first power supply terminal,  
       a fifth MOSFET having a source connected to the other terminal of the current source, and a gate connected to the first input terminal,  
       a sixth MOSFET having a source connected to the other terminal of the current source, and a gate connected to the second input terminal,  
       a seventh MOSFET having a drain and gate connected to a drain of the fifth MOSFET, and a source connected to the second power supply terminal, and  
       an eighth MOSFET having a drain connected to a drain of the sixth MOSFET, a gate connected to the gate and drain of the seventh MOSFET, and a source connected to the second power supply terminal.  
     
     
       6. A circuit according to  claim 2 , wherein said differential amplifier unit comprises 
       a current source having one terminal connected to the first power supply terminal,  
       a first bipolar transistor having an emitter connected to the other terminal of the current source, and a base connected to the first input terminal,  
       a second bipolar transistor having an emitter connected to the other terminal of the current source, and a base connected to the second input terminal,  
       a third bipolar transistor having a collector and base connected to a collector of the first bipolar transistor, and an emitter connected to the second power supply terminal, and  
       a fourth bipolar transistor having a collector connected to a collector of the second bipolar transistor, a base connected to the collector and base of the third bipolar transistor, and an emitter connected to the second power supply terminal.  
     
     
       7. A differential amplifier circuit comprising: 
       a differential amplifier unit which has first and second input terminals and differentially amplifies first and second input signals respectively input to the first and second input terminals;  
       a first voltage shift unit which is connected to a first external input terminal and the first input terminal, reduces a range of high to low levels of a first external input signal input from the first external input terminal, and supplies the resultant first external input signal as the first input signal to the first input terminal; and  
       a second voltage shift unit which is connected to a second external input terminal and the second input terminal, reduces a range of high to low levels of a second external input signal input from the second external input terminal, and supplies the resultant second external input signal as the second input signal to the second input terminal,  
       wherein said first voltage shift unit comprises:  
       a first MOSFET having a drain connected to a first power supply terminal, a gate connected to the first external input terminal, and a source connected to the first input terminal, and  
       a second MOSFET having a drain connected to the first input terminal, a gate which receives a first predetermined potential, and a source connected to a second power supply terminal,  
       wherein said second voltage shift unit comprises:  
       a third MOSFET having a drain connected to the first power supply terminal, a gate connected to the second external input terminal, and a source connected to the second input terminal, and  
       a fourth MOSFET having a drain connected to the second input terminal, a gate which receives the first predetermined potential, and a source connected to the second power supply terminal, and  
       wherein back gates of the first, second, third, and fourth MOSFETs are connected to the second power supply terminal.  
     
     
       8. A differential amplifier circuit comprising: 
       a differential amplifier unit which has first and second input terminals and differentially amplifies first and second input signals respectively input to the first and second input terminals;  
       a first voltage shift unit which is connected to a first external input terminal and the first input terminal, reduces a range of high to low levels of a first external input signal input from the first external input terminal, and supplies the resultant first external input signal as the first input signal to the first input terminal; and  
       a second voltage shift unit which is connected to a second external input terminal and the second input terminal, reduces a range of high to low levels of a second external input signal input from the second external input terminal, and supplies the resultant second external input signal as the second input signal to the second input terminal,  
       wherein said differential amplifier unit comprises:  
       a current source having one terminal connected to the first power supply terminal,  
       a fifth MOSFET having a source connected to the other terminal of the current source and a gate connected to the first input terminal,  
       a sixth MOSFET having a source connected to the other terminal of the current source and a gate connected to the second input terminal,  
       a seventh MOSFET having a drain and gate connected to a drain of the fifth MOSFET and a source connected to the second power supply terminal, and  
       an eighth MOSFET having a drain connected to a drain of the sixth MOSFET, a gate connected to the gate and drain of the seventh MOSFET, and a source connected to the second power supply terminal.  
     
     
       9. A differential amplifier circuit comprising: 
       a differential amplifier unit which has first and second input terminals and differentially amplifies first and second input signals respectively input to the first and second input terminals;  
       a first voltage shift unit which is connected to a first external input terminal and the first input terminal, reduces a range of high to low levels of a first external input signal input from the first external input terminal, and supplies the resultant first external input signal as the first input signal to the first input terminal; and  
       a second voltage shift unit which is connected to a second external input terminal and the second input terminal, reduces a range of high to low levels of a second external input signal input from the second external input terminal, and supplies the resultant second external input signal as the second input signal to the second input terminal,  
       wherein said differential amplifier unit comprises:  
       a current source having one terminal connected to the first power supply terminal,  
       a first bipolar transistor having an emitter connected to the other terminal of the current source and a base connected to the first input terminal,  
       a second bipolar transistor having an emitter connected to the other terminal of the current source and a base connected to the second input terminal,  
       a third bipolar transistor having a collector and base connected to a collector of the first bipolar transistor and an emitter connected to the second power supply terminal, and  
       a fourth bipolar transistor having a collector connected to a collector of the second bipolar transistor, a base connected to the collector and base of the third bipolar transistor, and an emitter connected to the second power supply terminal.  
     
     
       10. A circuit according to  claim 7 , wherein said differential amplifier unit comprises 
       a current source having one terminal connected to the first power supply terminal,  
       a fifth MOSFET having a source connected to the other terminal of the current source, and a gate connected to the first input terminal,  
       a sixth MOSFET having a source connected to the other terminal of the current source, and a gate connected to the second input terminal,  
       a seventh MOSFET having a drain and gate connected to a drain of the fifth MOSFET, and a source connected to the second power supply terminal, and  
       an eighth MOSFET having a drain connected to a drain of the sixth MOSFET, a gate connected to the gate and drain of the seventh MOSFET, and a source connected to the second power supply terminal.  
     
     
       11. A circuit according to  claim 7 , wherein said differential amplifier unit comprises 
       a current source having one terminal connected to the first power supply terminal,  
       a first bipolar transistor having an emitter connected to the other terminal of the current source, and a base connected to the first input terminal,  
       a second bipolar transistor having an emitter connected to the other terminal of the current source, and a base connected to the second input terminal,  
       a third bipolar transistor having a collector and base connected to a collector of the first bipolar transistor, and an emitter connected to the second power supply terminal, and  
       a fourth bipolar transistor having a collector connected to a collector of the second bipolar transistor, a base connected to the collector and base of the third bipolar transistor, and an emitter connected to the second power supply terminal.